Originally Posted by
Cadillac
The average rider will NOT ride 18-20 mph as Hezz suggests.
Instead, he/she would ride 18-20 kilometers per hour. (perhaps Hezz had a typo).
At 18-20 mph average a rider could do a century in 5 hours (or a little more) which is the goal of a lot of experienced riders.
170 km is just a shade more than a Century (161 km) and most new riders with some strength can do a century in about 8 to 10 hours.
The mtb tires will slow you down a little.
Perhaps I am not average. But I am 46 and still 40 pounds over weight. I do 60 miles (roughly 100 kilometer) In a little under four hours of riding time. I usually ride flat sections at 19-22 mph but hills and headwinds are a lot slower for me. Usually my average riding speed is between 16.5 - 18 mph with all the hills and slow sections averaged in for a generally flatish course with no really big climbs.
I figure a younger fit mountain biker should be able to ride at least as fast as I do on a road bike. With times adjusted for bike/tire setup.